1. Field of the Invention
The present invention relates to a method for imaging test objects by millimeter waves, in particular for inspecting individuals for suspicious objects, in which the test object is illuminated successively with millimeter waves along its circumference, and the scattered waves are received and analyzed to display an image of the test object. In addition, the invention concerns a device for carrying out the inventive method.
2. Description of the Background Art
In order to inspect individuals such as airline passengers for suspicious objects, such as weapons or explosives, metal detectors are used or the individuals are scanned by hand. Metal detectors have the disadvantage that they cannot detect any dangerous nonmetallic objects such as plastic weapons or explosives. Manual scanning is time-consuming and under certain circumstances is experienced as an invasion of privacy.
In order to eliminate these disadvantages, a variety of non-contacting monitoring systems have been proposed in which the individuals are scanned with millimeter waves in order to detect suspicious objects. U.S. Pat. No. 5,859,609 describes such a method in which the individual to be inspected stands on a platform while being successively illuminated along his circumference with millimeter waves from a vertical antenna array. To this end, the antenna array travels in a circle around the individual and scans him circumferentially. Electrical signals are produced at a variety of predetermined positions in space from the waves reflected from the target, and a computer generates a holographic reconstruction of the target from these signals. Similar methods are described in U.S. Pat. No. 5,455,590 and EP-A 0 925 517. The prior art devices for carrying out these methods require a complicated structure and are thus very expensive.